Treatment of ores



Patented Jan. 22, 1924.

were stares 1 51,431,351 arms.

ARTHUR- St DWIGHT, 01? NEW YORK, N. Y ASSIGNOB '1'0 DWIGHT & LLOYDMETALLURGICAL COMPANY, OF NEW YORK, N. Y.,' A. CORPORATION OF NEW JEY.

No Drawing.

To all whom it ma concern:

Be it known that ARTHUR S. DWIGHT, a citizen of the United States,residing at New York, in the county of New York and a State of New York,have invented certain new and useful Improvements in the Treatment ofOres, of which the following is a specification, reference being hadtherein to the accompanying drawing. his invention relates to animproved process for treating iron ore in such way that the iron can beobtained in sponge form without smelting, and in a superior condi-.tion.

The iron ores with which I have worked, in developing the invention,comprise, in the native conditions in which they are found, noton'lyiron in the form of oxide, but also other metals and elements suchas manganese, titanium, copper, sulphur, and

others, and these have prevented the obtaining of the iron in purecondition unless the ore is laboriously subjected to expensivetreatment. 4

In the ordinary treatment of iron ores to obtain the metal by areduction process (depending upon the use of a gaseous compound ofcarbon), the reactions involved are delicate .and easily halted andreversed. I 80 have found that the character of the reaction dependsupon the physical structure of the ore material. to be treated (that isas to whether it has a compact impervious structure that is highlyporous), and also upon 85 the relations toeach other of the compositionof the reducing gas, the temperature of the mass, and other conditions.

I havewalso found that if a reducing gas is employed whose initialefiicienc for suchan work is 100 per cent, it is rapi y lowered in its,efiiciency after commencing to come into contact with the oxides of ironat the temperatures which are favorable to the.

promotion of the reducing action. t For example, if a gas of the .watergas class namely, a mixture of carbon monoxide and hydrogen (CO-l-H) isused, the prod-- TREATMT 0F GEES;

Application. filed April as, 1922. Serial No; 557,377.

(CO-i-H)'is reduced to 70 per cent, or thereabouts (the other per centbeing the newly formed carbon dioxide and water vapor), the efliciencyof the reducing gas 7 may be regarded as terminated. In fact the gaseousbodynow becomes such that it tends to exert an oxidizing influence onthe metallic components. I shall refer to this ratio (of about 70 percent of the one and the 30 per cent of the. other) as the oint ofsaturation of the reducing gas. gas, after passing this point ofsaturation, is kept in contact with the metalliferous material, thereduction action not only will cease, but there is immediately atendency for the vmetalliferous components to revert to the originalhigher oxides.

This saturated gas volume, although no longer. efiicient as a reducingagent, and alf the.

though it .has become actively detrimental As to the degree oftemperature necessaryf for the reduction of the oxides of the metal tothe metals themselves: Itis to be noted that at a temperature of 700 C.,more or less, the oxides of iron can be reduced. And if the reducingtreatment inobtaining the iron can be carried on under properconditions, the iron can be selectively reduced without reducing theaccompanyin deleterious metallic bodies such as are or inarily reduced,together with the iron, under the high temperatures of the blastfurnace. And in the treatment of iron ore this selective reduction isone of the important matters which I have attained.

With the above matters noted, the process which I have perfected will bereadlly understood. I, first, preliminarily. prepare the ore in such waythat I can cause the reducing gas to rapidly pass through "a large massand, while doing so, enter intimately into all of the interior points ofthe mass and of its particles. I efiect this by preliminarily sinteringit. I commin le with the ore, in an approximately pu verulent condition,a quantity of pulverized carbon,

and then treat it in sintering apparatus in the manner set forth in myearlier patents, as Patent 1,254,316 granted me January 28, 1918. Theresult of the sinterin treatment is theproduction of a mass w 'ch is nottributed throu only porous, when considered as an entirety,

' operation gases are formed and freed at each oint in the mass, and asthe solid particles around each of these gas generating points are in anascent and more or less plastic condition, continuing for a briefperiod, the gas formation is instantly followed b the forming of theminute cell walls referred to which are uniformly disghout the ore body,and these permit a rapid entrance of the reducing gases in latertreatment.

After sintering, the product is, if necessary, broken, or physicallyreduced to particlesof sizes of, say, two-inch dimensions, an less.

A mass of :these sintered and porous ore particles is then introducedinto a suitable container and heated. After being heated a hot reducinggas is caused to pass through it. This gas is, with the exertion ofcare, made 100 per cent eflicient, or is brought as near to that pointas is possible in its re; ducing etliciency.v It is heated tothe properpoint for the reduction of iron, but the total heat in the ore mass(regarding both the heat in the ore itself and the heat of the gas) iskept at a point below that at which there will be a reduction of thedeleterious elements accompanying the iron. As soon as the gas with itsinitial efliciency comes into contact with the particles of oxide ofiron exposed at the cell walls in the porous sinter, the oxygen isseparated from the iron and increases the oxidation of the reducing gas;and this oxidizing of the gas, unless stopped, will, as above described,continue until the newly formed gas oxides again reactupon the metal,and the latter reverts to an oxide condition.

To avoid this result I so relate the total temperature in the ore massand'the length of the path for the reducing gas therethrough that assoon as the oint of saturation for the' gas is reached that is as soonas 30 per cent, or thereabouts, of its volume has become oxidized by theiron) I cause it to immediately escape from the ore body or from thatpart of the ore which is undergoing reducing treatment.

The result is a mass of ore in which the iron has been reduced to asponge condition without any of the deleterious elements beingmaterially affected; and by this process I produce an extremely pureiron,

Before exposing the ore to the air I prefer to abstract from it all oftheresidue heat which it may carry after the abovetreatment; for thispurpose passing it through a cooling region where it is brought down toordinary temperature. After such cooling it. can be'lndefinitelyexposed,

, superposed regions.

which highly heated rich introduced; that'is to say, have termed gas,which is 100 per cent, or-

Returning to the gas which, as above described, is Withdrawn from theore immediately after it is saturated:

This I take to a region where it can be burned in order that I may availmyself of the large quantity of heat that can be generated therefrom.This heat I utilize for preliminarily raising the temperature of the ore(prior to its coming into contact with the reducing gas) or raising thetemperature of the reduclng gas, or both. As already explained, thisgas, although its reducing efficiency becomes nil upon the addition of arelatively small amount of oxygen, is nevertheless susceptible of a muchhigher oxidation. I commingle air with it and burn it either in directcontact with an ore mass or in a combustion chamber from which the heatcan be imparted to the ore. Some ores may require a higher temperaturethan can be derived from the partially spent gas, and in such casessupplemental heating agencies are employed. But in many cases I havefound that not only can'the gas, after the reducing stage, be burned incontact with an ore mass, but that it can even be taken from this oretoa second combustion region and following can be had in mind:

Assume a vertical stack to the top of which the sintered and porous orecan be delivered by a bell and hopper charging device, the particles ofthe ore mass being preferably of the sizes above specified. Assumefurther that the chamber in the stack is divided into three well definedvertically The ore, as it descends, is heated to the required point inthe uppermost region. As it descends through the next the iron isreduced. As it descends through the third it is cooled by water jacketsor equivalent devices, and the iron sponge escapes at the bottom.

In the horizontal planes at the lower end of the second region are,tuyeres through gas, such as I thereabouts, efiicient.

- The gas immediately permeates the ore reducing gas is mass in thisregion, the second from the top.

There is no combustion or smelting action.

4 The ore has previous been highly heated, as

has been also the reducing gas. The depth of this region and thetemperatures of the ore and gas are such that by the time the gas hasreached the to of this second region and'passes up into the bottom ofthe upper region the gas has just reached its condition of saturation.Thatis to say, it has absorbed oxygen from the iron to a relativelysmall extent, 30 per cent, or thereabouts, of the gas volume beingoxidized,- the remaining 70 er cent still being in its initialconditlon. efore the oxidization of the gas becomes sufiicient to causea reoxidizing of the iron the gas passes into the upper region where itcommingles with the incoming ore mass. In the horizontal planes at thebottom of the upper region are tuyeres delivering air under blast ifnecessary. This commingles with the gas and the latter is ignited,generating a relatively high heat; but not sufiicient tosmelt any of thecom onents of the ore.

. en the burned gas reaches the top of the ore in the stack it is drawnofl' through exhaust ducts. If it be. still further combustible it istaken to stoves 'or burning chambers where its further combustion isutilized for the heatin of the reducing gas that is to be introduce atthe bottom of the reducing chamber.

It will be seen that in this way a continuous stream of ore can bepassing down the stack, it first becoming highly heated by thecombustion of the gas in contact with it; then passing through thereducing region where there is no combustion beyond the oxidizing of thegas by the iron. Finally the reduced sponge moves downward to thecooling chamber. And from the latter, af-

' ter bemg sufiiciently cooled, the sponge is discharged.

A delicate regulation of the temperatures of the ore and of the reducingas can be accomplished by any suitable evices. The length of the timeduring which the gas, whlle acting as an effective reducing agent,contacts with the ore, can be regulated in any suitable 'way.

To assist in attaining this delicate regulation I install pyrometers atthe critical points, and also instruments which indicate the exactconstitution of the gas from time to time. The close regulating ofconditions, which I practice, and which governs the reducing of theiron, on the one hand, and prevents the reducing of the variousaccomying metals and metalloids, on the other and, enables me to securethe selective reduction of the iron, for when I observe that from anycause (as the initial constitution of the gas, the character of the ore,the temperature of the mass in the reducing region, or the like) thereducing gas drops 1n its efficiency before it has passed throu h theentire ore mass, and is in danger o reoxidizing the metal, I cause itsescape by means'of by-passes', or equivalents, and introduce rich atproper points in compensation, al tough I the same purpose can beaccomplished in either of several ways. And the pyrometers, orequivalent indicators,

perature by b'y-passing some of the gas and to the hot blast stovesconducting it directly lfied W ove spec hen I or other apparatus a find,upon the contrary, that there is not enough fuel value in the saturatedgas to properly pre-heat the ore I introduce to the pre-heating regionsuflicient fresh, rich gas which I divert from the mains.

While I have mentioned one of the reducing gases commonly. employed, itis to be understood that numerous others are contemplated, such asacetylene and forms of rich hydrocarbon gas produced from oilorpulverized coal.

I have also mentioned 700 C., or there'- abouts, as the temperaturewhich, on the average, I have in mind relative to the reducing of theiron. But because of variations in the constitution of the ore, and fromother causes, this temperature may vary a number of degrees above andbelow the point specified. With such variations there should i be acorresponding variation in the conditions which I observe in carrying onmy treatment. At the lower temperatures a leanergas can be employed; asthe temperature rises a righer and richer' gas must be used, for at thehi her temperatures the oxidizing elements such as CO, and H 0) becomeascendant and stop the reducing action. The power of the oxidizingelements in the gas increases more rapidly than does that of thereducing elements as the temperature rises. a

I aim to keep it considerably below 1000 C. while reducing, and succeedin preventing the reducing of the bodies foreign to iron; this bein oneof the very disadvanta 'eous results 1n blast furnace treatment.

am aware that man methods have been proposed for direct re notion ofiron from its ores while they are in theirnative condi-- tion. And Ihave, myself, been largely occupied in the sintering of ores of thisclass to prepare them for blast furnace treatment.

perior to those obtained by any of the earlier methods of treatmentknown to me.

What I claim is:

1. The herein described method of treating ores containin oxides ofiron, it consisting in comming g with the ore a care bonaceous materaland sintering it to transform it into a highly porous bod then causing abody of reducing gas of re atively high mitial reducing efiiciency 'topass through and permeatethe' particles of said ore body while heated tothe point necessary for reducing, causing the iron to oxidize arelatively small proportion of the said gas, and then causing the saidbody of gas to immediately move out of contact with the ore particlesprior to the gas becoming efficient in reoxidizing the ore.

2. The herein described method of treating ores containing oxides ofiron, it consisting in commingling with the ore a carbonaceous materialand sintering it to transform it into a highly porous body, then causinga body of reducing gas of relatively high initial reducing efiiciency topass through and permeate the particles of said ore while heated to theoint necessary for reducing, causing the iron to oxidize a relativelysmall proportion of the said gas, then causing the body of gas toimmediately move out of contact with the ore prior to the gas becomingefiicient in reoxidizing the iron, then causing the combustion of theescaping gas, and preliminarily heating other ore with the products ofthe combustion.

3. The herein described method of treating ores containing oxides ofiron, it consisting in subjecting the said ore to a sintering treatmentand forming thereof a body of ore particles which are all highly porousthroughout, then preliminarily heating a mass of the said ore, passingthrough the said heated mass a body of preliminarily heated reducing gaswhich is initially of relatively high reducing efiiciency, regulatingthe temperature. of the air while contacting with the reducing gas andthe time during which said contact occurs to prevent the gas from beingoxidized b the iron beyond the saturation point, an immediately causinga body of gas to pass out of contact with the ore mass before saidsaturation point is passed.

4. The herein described method of treatresist? ing ores containingoxides of iron, it consisting in commingling with the ore a combustiblematerial and sintering it to trans form it into a bodyof particles allof which are highly porous throughout, then causing reducing gas ofrelatively high initial reducing efiiciency to pass through said ore andcontact with the particles thereof, and causing the iron to oxidize arelatively small proportion of the said gas, then withdrawing the gasfrom the ore mass, then subjecting it to combustion, raising thetemperature of a supplemental ore mass by the heat of said combustion,and then causing supplemental reducing gas of initially high reducingefliciency to contact with the said supplemental ore mass.

5. The herein described method of treating ores containing oxides ofiron and also other metalliferous bodies, it consisting in comminglingwith the ore a combustible material and sintering it to transform itinto a mass of particles all of which are highly porous throughout, thenheating a body of said ore, causing a body of heated gas of relativelyhigh initial reducing efficiency to pass through and contact with theporous particles of the said ore bodies while heated to the pointnecessary for reducing, regulating the temperature of the ore inrelation to and while contacting with the reducing gas and in relationto the time during which said contact occurs, permitting the gas to beoxidized by the ore .to a predetermined relatively low degree,-

and to prevent the gas from reducing the metalliferous materials otherthan iron, and

immediately causing the gas to pass out of contact with the ore beforesaid degree of oxidation of the gas is passed.

In testimony whereof, I aflix my signature.

ART

